Circuit boards supporting a plurality of interconnected electric components to provide a variety of control voltages are well known. In many instances, these power supply assemblies supply the operating voltages for other circuit boards that are electrically interconnected in a rack assembly to form a programmable logic controller (PLC) that is normally used to control a number of functions in a manufacturing operation. This programmable logic controller is often of necessity located on the plant floor and thus is subject to considerable abuse.
The circuit boards of the power supply module are made of a nonmetallic material and are normally mounted in a sturdy housing external to the PLC. These assemblies are generally bulky and require mounting space. Further, wiring is required between the power supply and the PLC rack assembly. The circuit boards typically have various input/output devices must be outwardly exposed to permit operator monitoring and/or actuation. For example, circuit boards of this type can have an on-off switch, fuse holder, terminal blocks, battery, and a plurality of light emitting diodes (LEDs) that are outwardly exposed through windows formed in the housing wall. The on-off switch provides secured operation of the PLC. The terminal blocks are used for field wiring of input or output voltages. The LEDs provide a visual indication of the operation of the circuit board. In addition, the fuse provides protection from overloads of the supply voltages. The battery provides backup voltages for critical components in the PLC if a power outage occurs.
It is also well known that the circuit boards require frequent replacement when a malfunction occurs. Since a malfunction of necessity shuts down the machine operation, replacement must be made in a minimum amount of time.
The present invention provides a simplified rack mountable housing construction which easily accommodates the power supply circuit boards and also provides a novel cover which can be opened quickly to gain access to the electrical components on the circuit board.